Priority is claimed on Japanese Patent Application No. 2003-187303, filed Jun. 30, 2003, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a vehicle-mounted antenna composed of a slot antenna.
2. Description of Related Art
A planar antenna is known in the prior art, for example, that is equipped with a radiating conductor provided on the same surface on the interior side of a vehicle window glass and a roughly loop-shaped grounding conductor that surrounds the periphery of the edge of the radiating conductor at a location away towards the outside from the outer edge of the radiating conductor (see, for example, Japanese Unexamined Patent Application, First Publication No. 2002-252520).
In addition, a planar antenna is known that is equipped with a spacer that inclines the antenna so that the normal direction of the planar antenna approaches the vertical more than the normal direction of the mounting position of the planar antenna (e.g., vehicle window glass) in order to improve the reception sensitivity with respect to signals received from an artificial satellite at a relatively high elevation angle (see, for example, Japanese Unexamined Patent Application, First Publication No. Hei 5-63424).
However, when mounting a planar antenna according to the aforementioned prior art into a vehicle, in the case of arranging on a vehicle window glass such as the front windshield or rear window, it is desirable to prevent the field of view of the vehicle passengers from being obstructed, and also to prevent the appearance of the vehicle from being impaired.
However, if the dimensions, arrangement and so forth of a planar antenna are restricted based on vehicle appearance and so forth, there is the risk of it being difficult to obtain the desired transmission and reception characteristics. In the case a planar antenna has been provided on the surface of a vehicle window glass arranged so as to intersect the vertical direction in particular, there is the problem of it being difficult to ensure the desired transmission and reception reliability with respect to vertically polarized waves arriving from the horizontal direction.
In consideration of the aforementioned circumstances, the object of the present invention is to provide a vehicle-mounted antenna capable of inhibiting the loss of installability onto a vehicle while improving transmission and reception characteristics with respect to vertically polarized waves arriving from the horizontal direction.